This is quick and dirty, and I don't recommend it. hah! I'm also making a lot of assumptions here... Try this out for an example:
SELECT CONVERT(DATETIME, '19.03.2010', 103)
This will convert your European date/string to the american format. So then you can do this:
SELECT * FROM TableExample WHERE Date > CONVERT(DATETIME, '19.03.2010', 103)
If the problem is that the date could be in any number of formats, then you might think about running a cleaner once you have the data in the dataTable and then doing a table.Select.
The other option would be to clean the data in SQL and change the interface to only accept certain dates/formats. If you give users the chance to enter crap, they will.